The present invention relates to coordinated multi-point transmission and reception (CoMP) in wireless or mobile communications and, more particularly, to inter-eNB (E-UTRAN NodeB or eNodeB) CoMP with Network Assisted Interference Cancellation and Suppression (NAICS) and/or non-ideal backhaul (NIB).
The CoMP schemes that were discussed during the 3rd Generation Partnership Project (3GPP) Release 11 CoMP standardization assumed the availability of an ideal backhaul connecting the transmission points in each cluster. This assumption allowed for coordination within the cluster based on the instantaneous channel state information (CSI) reported by the users to those transmission points. Unfortunately, such schemes are far from being suitable when faced with a non-ideal backhaul that has a high latency. To guide the design of schemes that are appropriate for the NIB scenario, the following agreement was reached during 3GPP RAN1 (Radio Access Network Working Group 1 or Radio Layer 1) Meeting #74:
For each evaluated scheme, information relating to a transmission to/from a serving node in a given subframe should be categorized into two groups:
Group 1 information: information which is considered valid for a period longer than the backhaul delay, which may therefore be provided from a different node(s) from the serving node; and
Group 2 information: information which is considered valid for a period shorter than the backhaul delay, which must therefore be derived by the serving node.
The types of information may include for example:
CSI,
Allocated power per resource (including muting),
User equipment (UE) selection,
Precoding selection (including the number of transmit layers),
Modulation and coding scheme (MCS) selection,
Hybrid automatic repeat request (HARM) process number, and
Transmission point (TP) selection.
Transmission layers are sometimes called “transmit layers” or “layers.” The number of transmission layers is known as “transmission rank” or “rank.” A codebook is a set of precoding matrices or precoders. A precoding matrix is also known as a codeword.